In recent years, for example, in the fields of data centers, high-end computers (HPC) and so on, a transmission capacity and a transmission distance required for a communication band that is used are being increased. However, in the high-speed transmission using conventional electrical signal transmission systems, since the transmission distance and the transmission capacity have a trade-off relationship, the introduction of optical signal transmission systems is being progressed.
For example, in the communication standards such as Ethernet® and Infiniband, the standardization of systems using an optical transceiver of a multi-lane such as a 10 Gbps×4 lane, a 10 Gbps×12 lane or a 25 Gbps×4 lane is being progressed. For example, when the maximum amount of traffic is 100 Gbps, an optical transmission device is designed to use an optical transceiver of a 25 Gbps×4 lane. However, if actual network utilization efficiency is deteriorated, unnecessary power is wastefully consumed. Therefore, the wasteful power consumption may be reduced by adjusting the number of lanes used, for example, by reducing the number of lanes unused, depending on the actual amount of traffic. At this time, by transmitting use lane information, such as the number of lanes used, as control information between optical transmission devices, it is possible to adjust the number of lanes used, depending on the actual network utilization efficiency.
References listed below disclose techniques for transmitting control information between optical transmitters. Japanese Laid-Open Patent Publication No. 2014-045370 discloses a method for transmitting control information carried on a digital signal which is an ON/OFF optical main signal. An optical transmitter transmits the ON/OFF optical main signal carrying control information such as use lane information, to an opposing optical transmitter. The opposing optical transmitter may use a loss of signal (LOS) function that detects signal disconnection to detect the control information from the ON/OFF main signal.
Japanese Patent No. 5351689 discloses a method for transmitting a control frame of control information such as, for example, an operation administration and maintenance (OAM) frame, to be inserted between data frames. That is, an optical transmitter may transmit the control information at the same bit rate as data. Japanese Laid-Open Patent Publication No. 2010-263610 discloses a method for transmitting control information added with a header in order to distinguish between transmission frame data and the control information.
Related techniques are disclosed in, for example, Japanese Laid-Open Patent Publication No. 2014-045370, Japanese Patent No. 5351689 and Japanese Laid-Open Patent Publication No. 2010-263610.